*{
    margin: 0;padding: 0;
}
.box{
    width: 100px;
    height: 100px;
    background-color: aquamarine;
    padding: 10px;
    border: 5px solid pink;
    margin: 1px;
    /* 边框总体大小or其他的另算
    box-sizing: border-box or content-box; */
}
/* 边框三角形 */
.sanjiao{
    margin-top: 20px;
    height: 0px;
    width: 100px;
    border-top: 20px solid white;
    border-left: 20px solid white;
    border-bottom: 20px solid white;
    border-right: 20px solid darkblue;
}
/* 胶囊（圆角） */
.circle{
    width: 50px;
    height: 100px;
    background-color: yellowgreen;
    border-radius: 25px;
}